1. Field of the Invention
The present invention relates generally to a heat exchanger, and more particularly, to heat medium conducting elements which form a heat exchange region of a heat exchanger.
2. Description of the Prior Art
A heat exchanger, as illustrated in FIG. 1, is well known in the art, for example, U.S. Pat. No. 5,348,083. As shown in FIG. 1, a heat exchanger, such as condenser 100, includes a plurality of adjacent, substantially flat tubes 110 having oval cross-sections and open ends which allow refrigerant fluid to flow therethrough. A plurality of corrugated outer fin units 120 are fixedly disposed between adjacent flat tubes 110. Flat tubes 110 and fin units 120 form a heat exchange region 100a, at which an exchange of heat occurs. Cylindrical header pipes 130 and 140 having top and bottom open ends are disposed perpendicular to flat tubes 110. Partition plate 131 is disposed at an upper location within header pipe 130. An upper plug 132 is disposed in the top open end of header pipe 130, and a lower plug 133 is disposed in the bottom open end of header pipe 130. Partition wall 131, upper plug 132, and lower plug 133 divide header pipe 130 into upper fluid chamber 130a and lower fluid chamber 130b. Inlet pipe 150 extends into header pipe 130 and links upper fluid chamber 130a with other elements of the refrigerant circuit, e.g., a compressor (not shown). The two chambers 130a and 130b are isolated from each other.
Header pipe 140 includes a partition wall 141 disposed therein. Partition wall 141 is located within header pipe 140, but preferably below the location of partition wall 131 within header pipe 130. Upper plug 142 and lower plug 143 are disposed in the top open end and the bottom open end of header pipe 140, respectively. Partition wall 141, upper plug 142, and lower plug 143 divide header pipe 140 into upper fluid chamber 140a and lower fluid chamber 140b, each of which is isolated from the other. Outlet pipe 160 extends into header pipe 140 and links lower fluid chamber 140b with other elements of the refrigerant circuit, e.g., an accumulator (not shown). Flat tubes 110 having open ends are fixedly and hermetically connected to the inside of header pipes 130 and 140, so as to be in communication with the hollow interiors of header pipes 130 and 140.
In other prior art, such as Registered Japanese Design Patera No. 709839, a flat tube, substantially as illustrated in FIG. 2, is disclosed. Each of the flat tubes of condenser 100, which are illustrated in FIG. 1, may be replaced with the flat tube illustrated in FIG. 2.
Referring to FIG. 2, flat tube 210 includes flat tube member 211 and a plurality of projected stripes 212 integrally formed along an upper and a lower inner surface of flat tube member 211. Projected stripes 212 have substantially rectangular cross-sections and extend longitudinally along the inner surfaces of flat tube member 211. Projected stripes 212 are spaced from one another at about equal intervals. Thus, projected stripes 212 function as inner fins of flat tube 210. Flat tubes 210 further include a plurality of, e.g., three, partition walls 213. Partition walls 213 are integrally formed along the inner surfaces of flat tube members 211. Partition walls 213 extend longitudinally along flat tube members 211 and divide the interior of hollow portions of flat tube members 211, for example, into two rectangular parallel-piped hollow regions 214 and a pair of semiclyindrical hollow portions 215 located at the lateral ends of each flat tube member 211. Hollow regions 214 and 215 extend parallel to one another. However, as discussed below, these hollow regions extend transversely relative to a flow direction "A" of the air, which flows across the exterior surfaces of the flat tube 210.
During operation of a refrigerant circuit including condenser 100 having a plurality of flat tubes 210, such as those illustrated in FIG. 2, the discharged refrigerant gas from a compressor is directed into upper fluid chamber 130a of header pipe 130 via inlet pipe 150. The refrigerant gas directed into upper fluid chamber 130a of header pipe 130 flows downwardly through upper fluid chamber 130a of header pipe 130. As the refrigerant gas flows downwardly through upper fluid chamber 130a of header pipe 130, it concurrently flows into hollow regions 214 and 215 of each of flat tubes 210 in the upper section of the heat exchange region 100a of condenser 100. Referring to FIG. 1, the gas then flows longitudinally from the left to the right side of condenser 100 through hollow regions 214 and 215 of each of the flat tubes 210 in the upper section of the heat exchange region 100a. The refrigerant gas in each of flat tubes 210 exchanges heat with air passing across corrugated fins 210 and liquefies. The flow direction of the air passing through condenser 100 is indicated by arrow "A" in FIG. 1. Accordingly, the air flows laterally across the exterior surface of flat tubes 210.
The refrigerant flows through hollow regions 214 and 215 of each of flat tubes 210 in the upper section of the heat exchange region 100a of condenser 100 and into upper fluid chamber 140a. This refrigerant flows downwardly through upper fluid chamber 140a of header pipe 140. Referring again to FIG. 1, the refrigerant then flows longitudinally from the right to the left side of condenser 100 through hollow regions 214 and 215 of each of the flat tubes 210 in a middle section of the heat exchange region 100a. Gaseous refrigerant remaining in each of flat tubes 210 exchanges heat with air passing across corrugated fins 120 and liquifies.
The refrigerant flowing through hollow regions 214 and 215 of each of flat tubes 210 in the middle section of the heat exchange region 100a of condenser 100 flows into lower fluid chamber 130b of header pipe 130 and downwardly through lower fluid chamber 130b of header pipe 130. Referring once again to FIG. 1, the refrigerant then flows longitudinally from the left to the right side of condenser 100 through hollow regions 214 and 215 of each of the flat tubes 210 in a lower section of the heat exchange region 100a. Again, gaseous refrigerant remaining in each of flat tubes 210 exchanges heat with air passing across corrugated fins 120 and liquefies.
The refrigerant flowing through hollow regions 214 and 215 of each of the flat tubes 210 in the lower section of the heat exchange region 100a of condenser 100 flows into lower fluid chamber 140b of header pipe 140. The refrigerant in lower fluid chamber 140b of header pipe 140 has been completely liquefied and is conducted to an accumulator (not shown) or other component of the refrigerant circuit via outlet pipe 160.
According to the prior art embodiment depicted in FIG. 2, the integral formation of partition walls 213 with flat tube member 211 prevents improper expansion of flat tube members 211 caused by the pressure of the refrigerant in flat tube 210. Thus, flat tube 210 may sufficiently resist the internal pressure forces of the refrigerant. Further, by forming projected stripes 212 and partition walls 213, the surface area with which the refrigerant comes in contact as it flows through flat tubes 210 increases, so that the heat exchanging performance of condenser 100 increases.
Nevertheless, during operation of the refrigerant circuit, the refrigerant in each of flat tubes 210 flows along projected stripes 212 and partition walls 213, so that the refrigerant flows through each of flat tubes 210 in a flow condition similar to a laminar flow condition. As a result, a thermal gradient occurs in the refrigerant which flows through flat tube 210. Referring to FIG. 2, due to this thermal gradient, the temperature of the refrigerant located at the leading portion of flat tube 210 becomes lower than that at the trailing portion of flat tube 210. Thus, the temperature of the refrigerant flowing through flat tube 210 is not uniform with respect to the lateral direction, i.e., the direction parallel to air flow direction "A", of flat tube 210. This thermal gradient in the refrigerant in flat tube 210 decreases the heat exchanging performance of condenser 100.